This proposal is submitted in response to RFA-AI-08-001. Our proposal targets the development of therapy against hemolytic uremic syndrome (HUS) caused by Shiga toxin (Stx)-producing E. coli (STEC). STEC strains are serious Category B pathogens associated primarily with food and waterborne acquired disease. They represent an important global emerging infection with relevance to foodborne illness and potential bioterrorism. The virulence of STEC is underscored by the very low infectious dose required to produce clinical disease. The treatment of STEC infection is complicated by potentially adverse consequences of routine administration of antibiotics. Diarrhea-associated (HUS) is a life-threatening complication of STEC infection, primarily the O157:H7 serotype, in children and the elderly that is heralded by the sudden onset of pallor and oliguria. It is associated with significant morbidity and, despite improvements in pediatric intensive care;the mortality rate from this disease remains 3-5%. There is no proven therapy for HUS that reduces mortality, the need for acute dialysis, or the occurrence of serious extra-renal events. The recent outbreaks, the spinach outbreak in particular, showed how vulnerable the population is to accidental contamination, and how urgently protective or therapeutic measure are needed. In this application we propose to use the newly developed aptamer technology which has gained foot as potential therapeutic agents in several systemic diseases in humans. In this application two teams have come together to achieve the goals of this application. They include a team with expertise in the design, synthesis and application of aptamer technology, and a team with expertise on STEC disease and the development screening and in vitro and in vivo evaluation of therapeutic agents against HUS. Consequently: Specific Aim 1 focuses on the design, synthesis and optimization of aptamers, Specific Aim 2 will apply ELISA and cell-based assays for screening of aptamers. Specific Aim 3 will evaluate in the mouse toxicity model selected aptamers generated from the cell based screening, including drug toxicity and pharmacokinetics, while Specific Aim 4 will perform preclinical evaluation and pharmacokinetics in the well-established piglet model of E. co//O157:H7 infection/systemic intoxication model. RELEVANCE (See instructions): Infection of children with Shiga toxin (Stx) producing Escherichia coli (STEC), primarily a food and waterborne acquired disease, is the leading cause of hemolytic-uremic syndrome (HUS) in the US. There is no specific treatment to prevent or ameliorate HUS. In this proposal, we propose to develop aptamer-based therapeutic agents for prevention or treatment of HUS.